/Engine/Source/Developer/CollectionManager/Public/ICollectionManager.h
Note: Generally you won't need to save collections manually as the collection manager takes care of that as objects and added/removed, etc. however, you may want to manually save a collection if a previous save attempt failed (and you've since corrected the issue), or if the collection contains redirected object references that you'd like to save to disk.
true if the save was successful. If false, GetLastError will return a human readable string description of the error.
bool SaveCollection ( [FName](API\Runtime\Core\UObject\FName) CollectionName, [ECollectionShareType::Type](API\Developer\CollectionManager\ECollectionShareType\Type) ShareType )